Prompt gamma activation analysis as a means for quantitative, non-destructive, non-invasive measurement of mercury in steel from oil and gas operations

Prompt Gamma Neutron Activation Analysis (PGAA or PGNAA) is a non-destructive elemental analysis method potentially applicable for the non-invasive measurement of wall-bound mercury (Hg) deposited at trace levels on the process wetted surface of steel pipe and vessels in oil and gas production and processing. Total wall-bound mercury, on 17 mercury-impacted steel coupon samples was measured by two non-destructive methods: PGAA and XRF (X-ray Fluorescence spectroscopy). Following the non-destructive measurement methods, the samples were digested and analyzed by an Atomic Fluorescence Spectroscopy method based on the principles of EPA 1631 method (Acid Digest-AFS), generally considered state of the art for accurate mercury in steel measurements. PGAA and XRF results were compared to those from the modified EPA 1631 method. Comparative analysis of the results indicated that the PGAA measurements exhibited a trend relatively like that of the acid digest-AFS method measurements. Measurement accuracy, as determined by comparison to a "standard method" (Modified EPA 1631) was not yet adequate for quantitative measurement. However, the consistency in the tracking of the PGAA results with results from the "standard method" along with derivation of a self-attenuation correction factor suggests the potential for improved accuracy and correlation. Details of the intercomparison are provided herein.